The North Dakota oil boom has resulted in more trains going boom. At least 10 trains hauling crude oil from the Bakken Shale across North America have derailed and spilled, often setting off explosions. The deadliest killed 47 people in Lac-Mégantic, Quebec, on July 6, 2013. As California refineries seek to adapt their operations to bring in Bakken crude by rail, Bay Area residents in refinery towns want to know: Will they be safe?

In Solano County, Benicia residents packed a Planning Commission meeting when Valero Refining Co. unveiled a plan to adapt its Benicia refinery to receive crude by rail rather than by ship. In Contra Costa County, Pittsburg residents (as well as state Attorney General Kamala Harris) are concerned about a proposal by West Pac Energy to convert a closed tank farm to an oil storage and transfer facility. Similar worries are voiced in Crockett and Rodeo about a proposed propane and butane project at the Phillips 66 refinery.

Air pollution is the top-line concern for these communities, followed by fear of spills and explosions. Some protests are tied to the larger political debate over importing tar sands oil from Canada.

We do know this: The tangle of laws and agencies that oversee rail transport make it easy to assign blame to someone else and tough to hold any one agency or business accountable. Rail oversight is primarily the federal government's job, which makes sense for an industry with track in every state. While the state handles pollution, some safety inspections and emergency response, it is unclear how much legal authority it or any other state government has. The Obama administration announced some voluntary safety measures Friday that would slow trains in cities, increase track inspections and beef up emergency response. There's still work to do be done sorting out who would enforce such rules.

We need to know how theses railroads will run safely before more Bakken crude comes in by rail.

More crude riding the rails

85-fold - the increase in the amount of crude oil transported on U.S. railroads since 2006, from 4,700 carloads to 400,000 carloads in 2013, according to a rail industry regulatory filing.

135 times - the increase in the amount of crude transported by rail in California since 2009, from 45,491 barrels in 2009 to 6,169,264 barrels in 2013, according to the California Energy Commission.

1 percent - the portion of crude oil transported into California by rail (most comes by ship). This is projected to increase as more refineries adapt to bring in Bakken crude by rail.

73 degrees Fahrenheit - the flash point of Bakken crude, a lighter oil that contains more volatile organic compounds than other crude oils, as compared with 95 degrees Fahrenheit. "Crude oil being transported from the Bakken region may be more flammable than traditional heavy crude oil," reported the U.S. Department of Transportation.